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<title>Chapter 6. Boost.Circular Buffer</title>
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<div><h2 class="title">
<a name="circular_buffer"></a>Chapter 6. Boost.Circular Buffer</h2></div>
<div><div class="authorgroup"><div class="author"><h3 class="author">
<span class="firstname">Jan</span> <span class="surname">Gaspar</span>
</h3></div></div></div>
<div><p class="copyright">Copyright © 2003-2013 Jan Gaspar</p></div>
<div><div class="legalnotice">
<a name="circular_buffer.legal"></a><p>
        Distributed under the Boost Software License, Version 1.0. (See accompanying
        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
      </p>
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<div class="toc">
<p><b>Table of Contents</b></p>
<dl class="toc">
<dt><span class="section"><a href="circular_buffer.html#circular_buffer.intro">Introduction</a></span></dt>
<dt><span class="section"><a href="circular_buffer/example.html">Circular_buffer example</a></span></dt>
<dt><span class="section"><a href="circular_buffer/rationale.html">Rationale</a></span></dt>
<dt><span class="section"><a href="circular_buffer/implementation.html">Implementation </a></span></dt>
<dt><span class="section"><a href="circular_buffer/examples.html">More Examples</a></span></dt>
<dt><span class="section"><a href="circular_buffer/headers.html">Header Files</a></span></dt>
<dt><span class="section"><a href="circular_buffer/concepts.html">Modelled Concepts</a></span></dt>
<dt><span class="section"><a href="circular_buffer/template_params.html">Template Parameters</a></span></dt>
<dt><span class="section"><a href="circular_buffer/tickets.html">Trac Tickets</a></span></dt>
<dt><span class="section"><a href="circular_buffer/release.html">Release Notes</a></span></dt>
<dt><span class="section"><a href="circular_buffer/acknowledgements.html">Acknowledgements</a></span></dt>
<dt><span class="section"><a href="circular_buffer/version_id.html">Documentation Version Info</a></span></dt>
<dt><span class="section"><a href="boost_circular_buffer_c___reference.html">Boost.Circular_buffer C++ Reference</a></span></dt>
<dd><dl>
<dt><span class="section"><a href="boost_circular_buffer_c___reference.html#doxygen.boost_circular_buffer_c___reference.circular__buffer_8hpp">Header &lt;boost/circular_buffer.hpp&gt;</a></span></dt>
<dt><span class="section"><a href="boost_circular_buffer_c___reference.html#doxygen.boost_circular_buffer_c___reference.base_8hpp">Header &lt;boost/circular_buffer/base.hpp&gt;</a></span></dt>
<dt><span class="section"><a href="boost_circular_buffer_c___reference.html#doxygen.boost_circular_buffer_c___reference.space__optimized_8hpp">Header &lt;boost/circular_buffer/space_optimized.hpp&gt;</a></span></dt>
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<dt><span class="section"><a href="circular_buffer/s14.html">Index</a></span></dt>
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<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../doc/src/images/note.png"></td>
<th align="left">Note</th>
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      A printer-friendly PDF version of this manual is also available.
    </p></td></tr>
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<div class="section">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="circular_buffer.intro"></a><a class="link" href="circular_buffer.html#circular_buffer.intro" title="Introduction">Introduction</a>
</h2></div></div></div>
<p>
      A Circular Buffer.
    </p>
<h3>
<a name="circular_buffer.intro.h0"></a>
      <span class="phrase"><a name="circular_buffer.intro.description"></a></span><a class="link" href="circular_buffer.html#circular_buffer.intro.description">Description</a>
    </h3>
<p>
      The term <a href="http://en.wikipedia.org/wiki/Circular_buffer" target="_top">circular
      buffer</a> (also called a <span class="emphasis"><em>ring</em></span> or <span class="emphasis"><em>cyclic
      buffer</em></span>) refers to an area in memory which is used to store incoming
      data. When the buffer is filled, new data is written starting at the beginning
      of the buffer and overwriting the old.
    </p>
<p>
      <code class="computeroutput"><a class="link" href="doxygen/boost_circular_buffer_c___reference/classboost_1_1circular__buffer.html" title="Class template circular_buffer">boost::circular_buffer</a></code>
      is a STL compliant container.
    </p>
<p>
      It is a kind of sequence similar to <a href="https://www.boost.org/sgi/stl/List.html" target="_top">std::list</a>
      or <a href="https://www.boost.org/sgi/stl/Deque.html" target="_top">std::deque</a>.
      It supports random access iterators, constant time insert and erase operations
      at the beginning or the end of the buffer and interoperability with std algorithms.
    </p>
<p>
      The <code class="computeroutput"><a class="link" href="doxygen/boost_circular_buffer_c___reference/classboost_1_1circular__buffer.html" title="Class template circular_buffer">circular_buffer</a></code> is
      especially designed to provide <span class="bold"><strong>fixed capacity</strong></span>
      storage. When its capacity is exhausted, newly inserted elements will cause
      elements to be overwritten, either at the beginning or end of the buffer (depending
      on what insert operation is used).
    </p>
<p>
      The <code class="computeroutput"><a class="link" href="doxygen/boost_circular_buffer_c___reference/classboost_1_1circular__buffer.html" title="Class template circular_buffer">circular_buffer</a></code> only
      allocates memory when created, when the capacity is adjusted explicitly, or
      as necessary to accommodate resizing or assign operations.
    </p>
<p>
      <span class="inlinemediaobject"><img src="../../libs/circular_buffer/doc/images/circular_buffer.png"></span>
    </p>
<p>
      There is also a <code class="computeroutput"><a class="link" href="doxygen/boost_circular_buffer_c___reference/classboost_1_1circular__buffer__space__optimized.html" title="Class template circular_buffer_space_optimized">circular_buffer_space_optimized</a></code>
      version available.
    </p>
<p>
      <span class="inlinemediaobject"><img src="../../libs/circular_buffer/doc/images/space_optimized.png"></span>
    </p>
<p>
      <code class="computeroutput"><a class="link" href="doxygen/boost_circular_buffer_c___reference/classboost_1_1circular__buffer__space__optimized.html" title="Class template circular_buffer_space_optimized">circular_buffer_space_optimized</a></code>
      is an adaptation of the <code class="computeroutput"><a class="link" href="doxygen/boost_circular_buffer_c___reference/classboost_1_1circular__buffer.html" title="Class template circular_buffer">circular_buffer</a></code>
      which <span class="bold"><strong>does not allocate memory all at once when created</strong></span>,
      instead it allocates memory as needed.
    </p>
<p>
      The predictive memory allocation is similar to typical <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span></code>
      implementation. Memory is automatically freed as the size of the container
      decreases.
    </p>
<p>
      The memory allocation process of the space-optimized circular buffer. The
      <code class="computeroutput">min_capacity</code>
      of the capacity controller represents the minimal guaranteed amount of allocated
      memory. The allocated memory will never drop under this value. The default
      value of the <code class="computeroutput"><span class="identifier">min_capacity</span></code> is
      set to 0. The <code class="computeroutput"><span class="identifier">min_capacity</span></code>
      can be set using the constructor parameter <code class="computeroutput">()
      capacity_control </code> or the function <code class="computeroutput"><span class="identifier">set_capacity</span></code>.
    </p>
<p>
      The space-optimized version is, of course, a little slower.
    </p>
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